Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
H,W = map(int,input().split())
S =[]
for _ in range(H):
    a = input()
    S.append(a)
count =0
for i in range(H):
    for j in range(W):
        if S[i][j] =='.':
            count += 1
from collections import deque

seen = [[False]*(W) for _ in range(H)]
seen[0][0] = True
dq = deque([(0,0,1)])
d = [(1,0),(0,1),(0,-1),(-1,0)]
while dq:
    x,y,cnt = dq.popleft()
    if x ==H-1 and y ==W-1:
        print(count-cnt);exit()
    for dx,dy in d:
        if 0<=x+dx<H and 0<=y+dy<W and seen[x+dx][y+dy] ==False and S[x+dx][y+dy]=='.':
            seen[x+dx][y+dy] = True
            dq.append((x+dx,y+dy,cnt+1))
print(-1)